Calculi for higher order communicating systems

This thesis develops two Calculi for Higher Order Communicating Systems. Both calculi consider sending and receiving processes to be as fundamental as nondeterminism and parallel composition. The first calculus called CHOCS is an extension of Milner's CCS in the sense that all the constructions of CCS are included or may be derived from more fundamental constructs. Most of the mathematical framework of CCS carries over almost unchanged. The operational semantics of CHOCS is given as a labelled transition system and it is a direct extension of the semantics of CCS with value passing. A set of algebraic laws satisfied by the calculus is presented. These are similar to the CCS laws only introducing obvious extra laws for sending and receiving processes. The power of process passing is underlined by a result showing that the recursion operator is unnecessary in the sense that recursion can be simulated by means of process passing and communication. The CHOCS language is also studied by means of a denotational semantics. A major result is the full abstractness of this semantics with respect to the operational semantics. The denotational semantics is used to provide an easy proof of the simulation of recursion. Introducing processes as first class objects yields a powerful metalanguage. It is shown that it is possible to simulate various reduction strategies of the untyped λ-Calculus in CHOCS. As pointed out by Milner, CCS has its limitations when one wants to describe unboundedly expanding systems, e.g. an unbounded number of procedure invocations in an imperative concurrent programming language P with recursive procedures. CHOCS may neatly describe both call-by-value and call-by-reference parameter mechanisms for P. We also consider call-by-name and lazy parameter mechanisms for P. The second calculus is called Plain CHOCS. Essential to the new calculus is the treatment of restriction as a static binding operator on port names. This calculus is given an operational semantics using labelled transition systems which combines ideas from the applicative transition systems described by Abramsky and the transition systems used for CHOCS. This calculus enjoys algebraic properties which are similar to those of CHOCS only needing obvious extra laws for the static nature of the restriction operator. Processes as first class objects enable description of networks with changing interconnection structure and there is a close connection between the Plain CHOCS calculus and the π-Calculus described by Milner, Parrow and Walker: the two calculi can simulate one another. Recently object oriented programming has grown into a major discipline in computational practice as well as in computer science. From a theoretical point of view object oriented programming presents a challenge to any metalanguage since most object oriented languages have no formal semantics. We show how Plain CHOCS may be used to give a semantics to a prototype object oriented language called 0.Open Acess

Reduction of boar taint - the practical way

The aim of organic pig production is to ensure high animal welfare and natural products. Banning castration is thus a logical step forward, but the risk of boar taint in the meat is a major barrier for marketing meat from entire male pigs. Is it possible to use genetic tools and breeding strategies to prevent boar taint? What is the effect of feeding, management, housing and hygiene? Is it possible to process the meat to minimize the risk of boar taint? These issues will be discussed based on the results from the research project NOCAST, as well as other on-going Danish research projects on entire male pigs. Susanne Støier (DK): Boar taint – detection, consumer response and product quality Hanne Maribo (DK), Bent Borg (DK) and Rikke Thomsen (DK): Reduction of boar taint – the practical way. Anders Strathe (DK): Prevention of boar taint by means of genetics and breeding Theme 2: Outdoor production of growing-finishing pigs, provision of roughage / Chaired by Jan Tind Sørensen Use of roughage and outdoor production are two very important characteristics in organic livestock production. How does the use of roughage affect health and performance in growing-finishing pigs? Is it possible to encourage outdoor pigs to find a large part of their food directly in the field where they are kept, and how does this influence pig performance and meat quality? These issues will be discussed on the basis of results from two major research projects, SUMMER and ICOPP. Liisa Voutila (FI): Effect of roughage on pig health and performance Anne Grete Kongsted (DK) and Margrethe Therkildsen (DK): Outdoor growing-finishing pigs: effect of genotype and feeding strategy on animal behaviour, performance and meat quality Theme 3: Environmental impact and animal welfare / Chaired by Jan Tind Sørensen Robust and competitive organic pig production must minimise environmental impact as well as ensuring good animal health and welfare. In theory, improving animal health and welfare reduces environmental impacts through decreased medicine use, improved growth rates and feed conversion efficiency. Is it possible to verify these hypotheses on working farms? The relationship between animal health, welfare and environmental impact will be discussed based on the results from the Core organic II research project ProPig including data collection on these aspects on 75 organic pig farms across Europe. More specifically, it will also be discussed how management practices may affect parasite transmission and thus animal welfare within organic systems (PAROL and NOCAST projects). Christine Leeb (A): Assessment of animal welfare and environmental impact. Helena Mejer (DK): Parasite impact, transmission and control John Hermansen (DK): Introduction to group discussion

Hangrise lugter mere end forventet

Økologiske hangrise vokser godt, men mange har et højt niveau af stoffer, der giver ornelugt